1. FIELD OF THE INVENTION
The present invention relates to a die-bonding device for picking up a chip from a wafer set on a supply part of an electric part mounting machine and shifting and mounting the same onto a lead frame or a printed circuit board.
2. RELATED ART
In a die-bonding device, a nozzle picks up a chip under vacuum suction from a wafer set on a supply part of an electric part mounting machine, and then shifts and mounts the same onto a lead frame or a printed circuit board.
Explanation will be made of the above-mentioned die-bonding device with reference to FIG. 7 which is a side view. A lead frame 1 is held on a guide part 2 in an electric part mounting machine, and a wafer 3 is held on a holder 4 which is carried on a movable table device 7 composed of an X-axis table 5 and a Y-axis table 6. A head part 8 carrying thereon a nozzle 9 for picking up a chip P on the wafer 3 at its lower end under vacuum suction is adapted to be reciprocated between the wafer 3 and the lead frame 1 by a drive means (which is not shown).
The head part 8 is reciprocated between two positions, that is, a position indicated by a solid line and a position indicated by a chain line. When the head is located at the stop position indicated by the chain line, the movable table device 7 is operated so as to move the wafer 3 in the X-axial and Y-axial directions, relative to the nozzle 9 which therefore can pick up a desired chip P. With this arrangement, a height difference D is ensured between the wafer 3 and the guide part 2 in order to prevent the wafer 3 from interfering with the guide part 2 when the holder 4 for holding the wafer 3 is displaced toward the guide part 2, and the wafer 3 is located below the guide part 2.
In a condition in which the head part 8 comes to and stops at a position right above the wafer 3, as indicated by the chain line, a vertically moving means such as a linear motor incorporated in the head part 8, is driven, and accordingly, the nozzle 9 moves up and down so as to pick up a desired chip P from the wafer 3 under vacuum suction. When the head part 8 is shifted to and is stopped at the position indicated by the solid line above the lead frame 1, the nozzle 9 similarly moves up and down so as to mount the chip P onto the lead frame 1. The above-mentioned operational steps are repeated while the lead frame 1 is fed pitch by pitch on the guide part 2 so as to mount chips P picked up from the wafer 3, successively onto the lead frame 1.
Referring to FIG. 7, since the height difference D is ensured, a vertical stroke Sa of the nozzle 9 during pick-up of a chip P from the wafer 3, is longer than a vertical stroke Sb of the nozzle 9 during mounting of the chip P onto the lead frame 1. Accordingly, the vertical motion of the nozzle 9 for picking up a chip P from the wafer 3 requires a long time, and accordingly, there has been a problem such that a time tact becomes longer, correspondingly, and therefore, the working efficiency is low.
Further, the vertically moving means (such as a linear motor) for the nozzle 9, provided in the head part 8, is heavy in its weight which exerts a relatively large load when the head part 8 moves between the wafer 3 and the lead frame 1, and accordingly, an increase in shift speed of the head part 3 is limited.